Anorexia nervosa, a disorder of unknown etiology, is characterized by a disturbed body image, the marked diminution of food intake in the obsessive pursuit of thinness, a stereotypic rigidity and perfectionsism, and frequent mood and neuroendocrine disturbances. After weight restoration, there is reduced severity of these disturbances but they may not normalize. The relative contribution of neurotransmitter(s) abnormalities to the persistent pathophysiology is unclear. There are reasons to think that increased activity of brain serotonin pathways may be contributory. Our preliminary psychological data suggests that anxious and obsessional behavior is present at all stages of anorexia nervosa, but may be more pronounced after weight recovery. We will study underweight and short-term weight restored anorexics. We hypothesize that m-CPP administration will not produce anxiety and obsessive thinking in underweight anorexics and that such symptoms will be worse after stages of weight restoration.